One component of a liquid electrophotographic printing system is a developer roller. The developer roller is responsible for forming a uniform layer of ink as well as transporting an amount of ink onto a separate photoconductive surface. An ink layer is developed on developer roller surface through a high electric field. The photoconductive surface is typically on a cylinder often called a photo imaging plate (PIP). The photoconductive surface is selectively charged with a latent electrostatic image with image and background areas having different electrical potentials. Once the ink has been transferred to the separate surface, it may then eventually be transferred to a sheet of paper or other media thereby producing an image. For most transfer processes in an electrophotographic printing system, an electrical field is applied to electrically charged ink. The ink is charged such that it will be attracted to the photo imaging plate (PIP). The developer roller is made of a material capable of transferring this ink while also cooperating with other rollers within the electrophotographic printing system to achieve that goal. The material used for the developer roller establishes the quality of an image produced by the liquid electrophotographic printing system.
Developer rollers generally have a certain level of hardness, electrical conductivity, chemical stability, surface chemistry and morphology, and mechanical stability to interact appropriately with the rest of the components of the system. This is done so that the ink may be transferred to the photo imaging plate effectively and uniformly. However, attempting to fulfill all of the above mentioned criteria simultaneously may prove difficult and a manufacturer may have to settle on specific materials which may be more beneficial in one respect but not another.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.